Laser Eavesdropping

Project status

Some experiments have been conducted with photo transistor, 250mW laser, mirrors and a custom A-class amplifier. The device is not very sensitive. It can capture when people are talking near the window.

Further research should consider using modulated beam and either analogue demodulator, or direct sampling with something faster than a soundcard and then software-based demodulation.

The Laser Spy System is considered by many to be the Holy Grail of high tech spy devices because it can give the user the ability to listen in on conversations that take place in a distant building without having to install a bug or transmitter at the location. The Laser Spy System was said to be invented in the Soviet Union by Leon Theremin in the late 1940s. Using a non-laser based infrared light source, Theremin's system could detect sound from a nearby window by picking up the faint vibrations on the glass surface. The KGB later used this device to spy on the British, French and US embassies in Moscow. It is also interesting to note that Leon Theremin invented the world's first electronic instrument, a wand operated synthesizer named “The Theremin” after him. (quote)